This application is based on an application No. 2002-001795 filed in Japan, the content of which is hereby incorporated by reference.
(1) Field of the Invention
The present invention relates to a circuit layout of an integrated circuit device in which a 90-degree phase shifter is implemented. More particularly, the present invention relates to a technique for enhancing accuracy in phase difference between output signals.
(2) Description of the Related Art
Due to the expanding use of information and communications technologies such as the Internet, there is a growing demand for broader bandwidth in radio communications. As a result, there also is a great demand for 90-degree phase shifters that effectively operate at high frequencies. In addition, as typified by cellular phones, it is strongly desired to down-size radio communications devices. Consequently, it is required that a 90-dgeree shifter be small enough to be packed into an integrated circuit device.
To integrate a 90-degree phase shifter, for example, a 90-degree phase shifter having a circuit structure as shown in FIG. 2 is implemented on an integrated circuit device with a circuit layout as shown in FIG. 1.
FIG. 2 is a circuit diagram showing the circuit structure of a 90-degree phase shifter which receives a differential signal from an oscillator through an input terminal IN, and generates two differential signals having a 90-degree phase difference therebetween to output through two output terminals OUT1 and OUT2. FIG. 1 shows the circuit layout of the integrated circuit device at a portion corresponding to the 90-degree phase shifter.
Unfortunately, a conventional integrated circuit device as mentioned above has a problem. That is, when an input to the input terminal IN is made at high-frequencies of some GHz or higher, output signals from the output terminals OUT 1 and OUT 2 no longer have a 90-degree phase difference therebetween. Accordingly, it is said that the performance of a 90-degree phase shifter implemented as in a conventional manner is insufficient.
Here, it should be noted that even for the sake of eliminating the above problem, it is not desirable at all to upsize an integrated circuit device in which a 90-degree phase shifter is implemented in view of the above-mentioned demand for down-sizing radio communications devices.
In view of the above problem, an object of the present invention is to provide an integrated circuit device in which a 90-degree phase shifter is implemented in a manner that the 90-degree phase shifter accurately generates output signals with 90-degree phase difference therebetween even in high-frequency range. In addition, the above object must be achieved without upsizing the integrated circuit device.
The above-stated object is achieved by an integrated circuit device in which a 90-degree phase shifter is implemented. The 90-degree phase shifter includes four input capacitors all having equal capacitance and four output capacitors all having equal capacitance. Here, the input capacitors and the output capacitors are arranged alternately in a loop-shape array in plan view.
With this construction, wiring lengths of circuit components are made approximately all equal, and the wiring lengths are shortened. Consequently, it is achieved to suppress parasitic electromagnetic coupling between wires or between a wire and the circuit substrate, which leads to higher accuracy in output signals.
Note that the xe2x80x9cloop-shapexe2x80x9d is also referred to as an xe2x80x9cannular shapexe2x80x9d in the description below. The term xe2x80x9cannularxe2x80x9d used herein refers to any shape that forms a loop, and thus includes, for example, a ring shape, a square shape, and a rectangular shape as long as a line connecting the arranged circuit components draws a loop.
Further, each input capacitor may be connected to one of the output capacitors electrically in series without any other circuit component therebetween, and each input capacitor and an output capacitor connected to the input capacitor may be arranged next to each other in the loop-shape array.
With this construction, it is achieved to make wiring lengths of capacitors approximately equal and shorter. Consequently, accuracy of the 90-degree phase shifter is improved so that output signals are obtained with higher accuracy.
Further, the 90-degree phase shifter may include four input resistors and four output resistors, and the input resistors and the output resistors may be all arranged inside the loop-shape array.
With this construction, wiring lengths between a capacitor and a resistor as well as between resistors are made approximately all equal. In addition, the wiring lengths are shortened. Consequently, accuracy of the phase shifter is improved so that output signals are obtained with higher accuracy.
Further, each input resistor may be connected to one of the output resistors electrically in series without any other circuit component therebetween, and each input resistor and an output resistor connected to the input resistor may be arranged in spatial proximity to each other. Each input resistor may be spatially closer to an input capacitor than a corresponding output resistor is to the input capacitor.
With this construction, it is achieved to shorten wiring lengths between a capacitor and a resistor as well as between resistors that are directly related to each other. Consequently, accuracy of the phase shifter is improved.
Further, each input resistor may be connected to one of the output resistors electrically in series without any other circuit component therebetween, and each input resistor and an output resistor connected to the input resistor may be in spatial proximity to each other. Each output resistor may be spatially closer to an output capacitor than a corresponding input resistor is to the output capacitor.
With this construction, similarly to the above stated arrangement, it is achieved to shorten wiring lengths between a capacitor and a resistor as well as between resistors that are directly related to each other. Consequently, accuracy of the phase shifter is improved. In addition, the phase shifter is made compact, and thus the integrated circuit device in which the 90-degree phase shifter is implemented is made compact.
Further, the four input resistors may all have equal resistance, and the four output resistors may all have equal resistance.
With this construction, it is easier to adjust arrangement of the resistors within the area encircled by the loop-shape array of the eight capacitors, so that it is easier to make wiring lengths of circuit components approximately equal.
Further, as a concrete circuit structure, the 90-degree phase shifter may include an input loop circuit and an output loop circuit. The input loop circuit may be formed by the four input capacitors and four input resistors that are electrically looped in series in an order of a first input resistor, a first input capacitor, a second input resistor, a second input capacitor, a third input resistor, a third input capacitor, a forth input resistor, and a forth input capacitor. The output loop circuit may be formed by the four output capacitors and four output resistors that are electrically looped in series in an order of a first output resistor, a first output capacitor, a second output resistor, a second output capacitor, a third output resistor, a third output capacitor, a fourth output resistor, and a forth output capacitor. A node between the fourth input capacitor and the first input resistor may be electrically connected to a node between the first output resistor and the first output capacitor. A node between the first input capacitor and the second input resistor may be electrically connected to a node between the second output resistor and the second output capacitor. A node between the second input capacitor and the third input resistor may be electrically connected to a node between the third output resistor and the third output capacitor. A node between the third input capacitor and the fourth input resistor may be electrically connected to a node between the forth output resistor and the forth output capacitor. A node between the second input resistor and the second input capacitor may be electrically connected to a node between the forth input resistor and the forth input capacitor.
Alternatively, with a focus on the integration of a 90-degree phase shifter, the above-stated object of the present invention is achieved by an integrated circuit device in which a 90-degree phase shifter is implemented. The 90-degree phase shifter includes a plurality of capacitors and a plurality of resistors. Each of the plurality of capacitors is composed of a pair of electrodes. The pair of electrodes is arranged to be opposed to each other in a laminating direction. Each of the plurality of resistors is composed of a pair of electrodes. The pair of electrodes is arranged to be opposed to each other with a resistance film sandwiched therebetween. Here, the capacitors and the resistors together form an input shifter and an output shifter that are cascaded. The capacitors constituting the input shifter and the capacitors constituting the output shifter are alternately arranged in a loop-shape array in plan view. The resistors constituting the input shifter and the resistors constituting the output shifter are arranged inside the loop-shape array in radial symmetric relation.
With the stated implementation of a 90-degree phase shifter on the integrated circuit device, accuracy of the 90-degree phase shifter is improved.
Further, each capacitor constituting the input shifter may be taken as a pair with one of the capacitors constituting the output shifter and each pair of capacitors may be next to each other on the substrate. Each pair of capacitors may be connected to each other in series by a lower-positioned electrode of one capacitor being connected to an upper-positioned electrode of the other capacitor with a via.
With the stated implementation, a distance between capacitors arranged to be adjacent in the array is shortened, which achieves higher packing density.
Further, the loop-shape array in which the capacitors are arranged may be a square in plan view with the capacitors arranged three by three on each side of the square.
With the stated implementation, among three capacitors arranged on one side of the square, the capacitor in the middle is the one constituting the input shifter and arranged in proximity to an input resistor. Alternatively, the middle capacitor may be the one constituting the output shifter and arranged in proximity to an output resistor. Consequently, the overall wiring lengths are shortened, which leads to improve accuracy of the 90-degree phase shifter.
Further, the 90-degree phase shifter may include a square-shaped conductive land arranged centrally of the square area encircled by the capacitors. The resistors may be so arranged that each area between a side of the conductive land and a capacitor located outward the side includes two resisters connected to each other in series. Here, one of the two resistors may be a resistor constituting the input shifter and the other may be a resistor constituting the output shifter.
With the resistors arranged as stated above, it is achieved to shorten wiring lengths between resistors as well as between a capacitor and a resistor. Consequently, accuracy of the 90-degree phase shifter is improved.